1. Field of the Invention
The present invention relates to quality control testing and, more particularly, to a method of testing the objects in a set to obtain an increased level of quality.
2. Description of the Related Art
A manufacturing line commonly ends with a quality control review where the object being manufactured is checked to ensure that the object falls within accepted limits. The quality control review can be as simple as a visual inspection of a metal stamping, or as complex as the testing of a semiconductor die.
Whenever testing is involved in a quality control review, a range of acceptable test results must be determined. For example, the range of acceptable test results can be defined by a specification, such as 1 mV ±10%, or derived from specified limits. Once the range has been determined, the range does not change and becomes static.
Thus, when each object in a set of manufactured objects is tested, the result is compared to a static range of values that represents the test results which are acceptable. When the result falls within the static range of values, which is bounded by a static low limit and a static high limit, the object passes the test.
Another aspect of quality that is not typically measured on the manufacturing floor is reliability or, stated in another way, how long an object will continue to operate within the specified limits. In some industries, such as semiconductors, the operational lifetimes of a few of the die that pass the static testing are considerably shorter than permitted. This, in turn, can lead to expensive service calls.
Thus, to improve the overall quality of the manufactured objects, there is a need for a method of identifying objects which will have unacceptably shorter lifetimes, and remove these objects from inventory before they are delivered as manufactured objects.